大直径变截面钢管复合桩竖向承载性能研究∗

为了研究大直径变截面钢管复合桩竖向承载性能,选取鱼山大桥37#桩开展了自平衡试桩试验,并利用数值模拟软件ABAQUS对实际工况进行模拟,在验证了数值模型正确性的基础上对模型施加桩顶竖向荷载,分析了其桩身轴力与钢管应力传递规律,并通过改变变截面位置参数建立不同工况模型,分析了变截面位置对桩基竖向承载性能的影响。研究结果表明:自平衡试桩试验Q-s曲线没有突变较为平缓,经计算该桩单桩承载力为120 056kN,为单桩设计桩顶最大竖向荷载38 212 kN的3.14倍,桩基足够安全;数值模拟结果与实测较为吻合,数值模拟方法以及参数选取得当;变截面位置以上桩身轴力减小较缓,变截面处桩身轴力存在突变,变截面以下桩身轴力减小较快,桩端有端阻力存在,钢管处于弹性变形阶段并未屈服;变截面位置以上桩段越长桩基抵抗竖向变形能力越强,但生产实际中应考虑材料用量以达到最优。

Study on Vertical Load Bearing Performance of Large Diameter Steel Composite Pile with Variable Cross-section

To study the vertical load bearing capacity of large diameter steel composite pile with variable cross-section,a self-balanced pile test was carried out on 37# pile of Yushan bridge.The actual working condition is simulated by using the numerical simulation software ABAQUS.On the basis of verifying the correctness of the numerical model,the vertical load on the pile top was applied to the model,and the laws of axial force of the pile and the stress transfer of the steel pipe are analyzed.By changing the parameters of the variable cross-section positions,the models of different working conditions are established,and the influence of the variable cross-section positions on the vertical bearing capacity of the pile foundation is analyzed.The results show that:The Q-s curve of the self-balanced pile test had no abrupt change and was smooth.The bearing capacity of single pile is calculated to be120056 kN,which is 3.14 times of the maximum design vertical load of single pile,and the pile foundation is safe enough;The results of the numerical simulation are in good agreement with the measured data,which proves that the numerical simulation method and the selection of parameters are satisfactory;The axial force of the pile above the variable cross-section position decreases slowly,and there is a sudden change in the axial force of the pile at the position of variable cross-section.The axial force of the pile below the variable cross-section decreases rapidly,and the pile end resistance exists at the bottom of the pile.The steel pipe is in the stage of elastic deformation and does not yield;The longer the pile section above the variable cross-section position,the stronger the pile resistance to vertical deformation,but in actual production,the amount of material usage should be considered to optimize the design.